Homeostasis requires exchanging materials with

the environment.How do you do it?

Surfaces of contact with the environment let in oxygen and nutrients and excrete wastes.

The surface of contact between a cell and its environment is its plasma membrane.

Inside cell

Outside cell

Fluid Mosaic Model(description of membrane)

Cell/Plasma MembraneFluid Mosaic Model

• The cell, or plasma membrane is made of hydrophobic molecules called phospholipids.

• Proteins located in the membrane can flow/move and perform many functions, including receiving stimuli from the environment and transporting substances in and out of cell.

↓

The plasma membrane is semi-permeable / selectively permeable:

it controls what goes in/out of cell

Cell Membrane Diagram(add details as you go)

Phospholipid bilayer

Outside cell

Inside cell

Phospholipid Bilayer

Hydrophilic Phosphate Heads

HydrophobicTails

Inside of Cell

Outside of Cell

Saturated or Unsaturated?

Cell Transport movement of substances in and out of cell,

needed to maintain homeostasis

What substances does a cell need to move in and out?

Media Links For Lecture\08-02-MembraneStructure.mov

Water moves freely through aquaporins.O2 and CO2 move freely through membrane.

Polar particles need specialized carrier proteins:ions, glucose

Passive Transport 

Does not require the use of energy from ATP.(uses the kinetic energy in matter/stuff moving in/out)

Diffusion – Spreading of matter from one area to another. Matter always diffuses from areas of higher concentration to areas of lower concentration EQUILIBRIUM (same concentration everywhere)

Diffusion is “free” because stuff moves down/with a concentration gradient.

Ex.: food coloring spreading/mixing in water;

H2O, O2, CO2, monomer nutrients (some) moving in/out of cell

Movie TimeCell Membrane & Passive Transport

Mrs. Nordstrom:*press esc key (leave presentation mode),

then double click below*

08-02-MembraneStructure.mov

08-10-Diffusion.mov

Osmosis – Diffusion of water through a semi-permeable membrane.

Water flows from areas of lower solute concentration (+ water) to areas of higher solute concentration (- water).

Osmosis - Solution Concentration & Effect on Cells(show cells in a solution & net movement of water) Hypertonic Isotonic Hypotonic Very Hypotonic

Hypertonic Solution(Hypotonic Cell)

Is there a concentration gradient?

H 2O

PlasmolysisCell shrinks

(loses water)

Isotonic Solution(Isotonic Cell)

Is there a concentration gradient?

EquilibriumHappy cell

Hypotonic Solution(Hypertonic Cell)

Is there a concentration gradient?

Cell swells(gains water)

H2O

Very Hypotonic Solution

CytolysisCell lysis

Cell swells(gains water)

H2OH

2O H2O

08-11-Osmosis.mov

• Movie Time *

Osmosis ORThe Movement of Water Through a Semi-Permeable Membrane

Mrs. Nordstrom:*press esc key (leave presentation mode),

then double click below*

Glucose always use F.D.

Ions use F.D.

Facilitated Diffusion – requires the use of a carrier protein on the cell membrane (still no ATP energy needed).Ex.: glucose molecules, ions – why? Polarity…Protein channels are specific for the particles they move.

Carrier Protein / Ion Channel

Movie Time

Facilitated Diffusion IllustrationAt Colorado State Univ. Web Page

Turgid or Flaccid??

Salt Water

Hypoto

nic

Hypertonic

(Macroscopic Term)

Turgid or Flaccid??

Tap Water

HypotonicHyp

erton

ic

(Macroscopic Term)

A B C

Hypertonic -

Hypotonic -

Isotonic –

Prefix refers to the amount of Dissolved Solute (stuff)

Excess ‘stuff’........

Less ‘stuff’……….

Equal ‘stuff’…………

Osmosis Practice

Can you predict what will happen?

Think of water and solute concentrations.

Cell is 95% Water

Cell’s Environment is

90% waterWater Pushes Out

Osmosis

Cell is 95% Water

Cell’s Environment is

100% water

Water Pushes into Cell

Osmosis

Cell is 95% Water

Cell’s Environment is

95% water

EQUILIBRIUM

Osmosis

Cell is 95% Water

Cell’s Environment

is 90% water

The Cell is ___________The Cell’s environment is____________

HypotonicHypertonic

The Future Fate of the Cell might be toPLASMOLYZE

Osmosis

Cell is 95% Water

Cell’s Environment is 100% water

The Cell’s environment is____________The Cell is ___________

HypotonicHypertonic

The Fate of the Cell is Cytolysis

OsmosisCell is 95% Water

Cell’s Environment is 95% water

The Cell’s environment is____________The Cell is ________________________ISOTONIC

The Cell is at Equilibrium

Cyclosis

Plasmolysis

Which is more Plasmolyzed?Which might be further in the

process of re-hydrating?

Normal Plant Cell Isotonic Cell

Isotonic Environment

Hypotonic Cell

Hypertonic Env.

Hypertonic Cell

Hypotonic Env.

Plasmolysis Cytolysis

RBC in Isotonic Environment

The cell is also Isotonic

PlasmolysisCytolysis

Cell is Hypotonic, Env. is Hypertonic

Cell is Hypertonic, Env. Is Hypotonic

A B C

Simple Diffusion

Movement of ‘stuff’ down the Concentration Gradient through a semi-permeable cell membrane by Kinetic Energy

Media Links For Lecture\08-10-Diffusion.mov

Passive Transport1. Osmosis

2. Diffusion

3. Facilitated Diffusion - Glucose

4. Ion Channels

Movement of water in / out of cell

Movement of H2O, O2, CO2, Urea, monomer nutrients: either in / out of cell

Movement of Glucose (C6H12O6) into the cell. Helped by a specific Integrated Protein

Movement of ions in / out of cell, must go through specific integrated proteins